JP2847770B2 - Method for forming protective layer on end face of semiconductor laser cavity - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for forming a protective layer on a laser resonator end face necessary for high-power operation of a semiconductor laser, and more particularly to an etched mirror for forming a resonator end face by etching. The present invention relates to a method for forming a protective layer on an end face of a semiconductor laser resonator in a laser.

(Prior Art) Semiconductor lasers are widely used as light sources for optical communication and optical information processing. Short-wavelength semiconductor lasers used in light sources for optical information processing, etc., suffer from catastrophic optical damage (COD) edge destruction, which is a major problem in high-power operation. I have.

As the end face protective layer, a dielectric layer or a semiconductor film having a band gap larger than the photon energy is used.

On the other hand, an etched mirror laser is currently being researched and developed as a semiconductor laser having excellent mass productivity.

(Problems to be Solved by the Invention) However, if end faces are protected by a semiconductor layer in an etched mirror laser, the following problems occur. It is desirable that the laser cavity surface is formed perpendicular to the active layer of the semiconductor laser. However, if the edge protection of the etched mirror laser by the semiconductor layer is performed, the perpendicularity of the cavity surface to the active layer is lost. . FIG. 2 shows this state. FIG. 2 (a) shows a cross section of the resonator end face by etching. When the end face protective layer 6 is epitaxially grown on this end face, the perpendicularity to the active layer 2 is lost as shown in FIG. 2 (b). This is because, in the etched mirror laser, the end face of the resonator is connected to the bottom surface which is the etching stop surface, and the epitaxial growth of the semiconductor film on the end surface is affected by the epitaxial growth on the bottom surface.

An object of the present invention is to provide a method for forming a semiconductor end face protective layer in an etched mirror laser without losing the perpendicularity of the end face.

(Means for Solving the Problems) In order to achieve the above object, a method for forming a protective layer on the end face of a semiconductor laser resonator according to the present invention includes a double hetero structure comprising an active layer and a cladding layer formed on a semiconductor substrate. Forming a laser cavity by etching a semiconductor multilayer film; and forming the semiconductor layer or the semiconductor substrate closer to the semiconductor substrate side than the double hetero structure among the semiconductor layers exposed on the end face of the formed laser cavity. Forming a recess along a surface separating the semiconductor film formed on the end surface and the semiconductor film formed on the semiconductor substrate surface, and etching the laser cavity end surface and the inside of the cavity. A semiconductor having a larger forbidden band width than the active layer is vapor-phase epitaxially formed on the semiconductor layer or the semiconductor substrate etched in the direction. Forming the semiconductor layer grown by vapor phase epitaxial growth as a protective layer on the end face of the semiconductor laser cavity.

(Example) Next, the present invention will be described with reference to the drawings.

FIG. 1 is a view showing a method for forming an end face protective layer according to the present invention.

FIG. 1A is a cross-sectional view when a laser cavity is formed by etching, and a semiconductor layer 7 is inserted between a cladding layer 3 and a semiconductor substrate. This layer is a layer to be etched in the next step, and has a characteristic of being selectively etched with respect to the cladding layers 3 and 4 and the active layer 2.
If the semiconductor substrate has a selective etching characteristic, the semiconductor layer 7 is not particularly required.

FIG. 2 (b) shows a cross-sectional shape when etching is performed. The semiconductor layer 7 is etched toward the inside of the resonator. When vapor phase epitaxial growth is performed on the end face having such a cross-sectional shape, the influence of the epitaxial growth on the bottom face is small with respect to the epitaxial growth on the end face, and a uniform film thickness is grown on the end face for a while.
Therefore, an end face semiconductor protective layer 6 having an end face perpendicular to the active layer 2 is formed as shown in FIG. The concave portion formed inside the resonator formed by the semiconductor layer 7 separates the vapor phase epitaxial growth on the end face and the bottom face.

 Hereinafter, a specific example will be described.

After laminating a Ga _0.5 In _0.5 P layer 7 having a thickness of 2 μm on a GaAs substrate by metal organic chemical vapor deposition, a double heterostructure composed of AlGaAs and GaAs is laminated to produce a semiconductor laser wafer. In the figure, the active layer 2 and the cap layer 5 are GaAs, and the cladding layers 3 and 4 are AlGaAs layers. After that, a cavity end face is formed by reactive ion beam etching (RIBE). Next, etching is performed using a mixed solution of hydrochloric acid and water. At this time, the layer to be etched is Ga _0.5 In _0.5
Only the P layer 7 has a shape after etching as shown in FIG. Thereafter, a 0.2 μm-thick AlGaAs layer is stacked on the entire surface again by metal organic chemical vapor deposition to form a uniform thickness on the end face of the resonator, and the end face maintains perpendicularity to the active layer.

(Effect of the Invention) As described above, according to the present invention, it is possible to protect the end face of the etched mirror laser with the semiconductor layer without losing the perpendicularity of the end face to the active layer.

[Brief description of the drawings]

1 (a) to 1 (c) are views showing a method for forming a protective layer on the end face of a semiconductor laser resonator according to the present invention, and FIGS.
FIG. 2B is a diagram showing a conventional method for forming a cavity facet of a semiconductor laser. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Active layer, 3,4 ... Clad layer, 5 ... Cap layer, 6 ... End face protective layer, 10 ... Resonator end face.

Claims (1)

(57) [Claims] 1. A step of forming a laser resonator by etching a semiconductor multilayer film including a double heterostructure comprising an active layer and a cladding layer formed on a semiconductor substrate, and an end face of the formed laser resonator. The semiconductor layer or the semiconductor substrate closer to the semiconductor substrate than the double hetero structure among the semiconductor layers exposed to the substrate is etched toward the inside of the resonator, and the film formed on the end surface and the semiconductor layer or the semiconductor layer formed on the semiconductor substrate surface Forming a recess along a surface separating the film from the active layer, and forming a semiconductor having a larger forbidden band width than the active layer on the semiconductor layer or the semiconductor substrate etched toward the laser cavity end face and the cavity inside. The semiconductor layer grown by vapor phase epitaxial growth and the vapor phase epitaxial growth is used as a protective layer on the end face of the semiconductor laser resonator. Method of forming a semiconductor laser resonator end face protective layer, characterized in that it comprises the step of forming.